In this project we have been elucidating the physiology of a number of neural circuits which generate motor output patterns: one of these circuits is that of the flight control neurons in dipteran insects. In recent years we have extended this work to the fruit fly, Drosophila melanogaster. We already know much of the anatomy, physiology and connectivity of the 28 neurons which control flight. We are now interested in the mechanisms by which genes specify these properties. We propose to study the effect of mutations on the physiology and morphology of these cells. We will use a newly developed method for staining individual nerve cells with peroxidase which can be seen in both the light and electron microscope, and computer aided 3-dimensional reconstruction from serial section electron micrographs. We can determine alterations in the synaptic interactions by electrophysiological recording and stimulating of single cells. We will also use genetic mosaics where a neuron of mutant genotype grows a dendritic tree through normal neuropil, while its contralateral homolog is of normal genotype but grows its dendritic tree through mutant neuropil. Thus the effects of intracellular and extracellular factors on the growth of neurites may be assayed. From the knowledge of the alterations produced by mutant genes, we hope to elucidate the mechanism of action of the normal genes.